A wire electric discharge machining apparatus for machining a workpiece (7) by supplying current pulses to a work gap formed between a wire electrode (8) and the workpiece comprises a person detection sensor (10) for generating a person detection signal (EX) when the existence of a person is detected, and an NC device (20) that is configured to receive the person detection signal. When the NC device receives the person detection signal, it selects first machining conditions which improve machining speed. When the NC device does not receive the person detection signal, it selects second machining conditions which reduce the risk of wire breakage.